Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$250.45	10.152%	$275.8757	$275.88	$275.90	$275.90
Purchase #2	$47.32	10.421%	$52.2512	$52.25	$52.25	$52.30
Purchase #3	$27.90	3.730%	$28.9407	$28.94	$28.95	$28.90
Purchase #4	$94.45	4.720%	$98.908	$98.91	$98.90	$98.90
Purchase #5	$99.97	6.612%	$106.58	$106.58	$106.60	$106.60
Purchase #6	$221.44	5.259%	$233.0855	$233.09	$233.10	$233.10
Purchase #7	$78.71	10.662%	$87.1021	$87.10	$87.10	$87.10
7 purchase totals =	$820.24		$882.7432	$882.75	$882.80	$882.80